Hydrogen ion meter



Dec. 5, 1939. D' H. CAMERON HYDROGEN 10N METER Filed May 26, 1937 2 Sheets-Sheet 1 2 Sheets-Sheet 2 D. H, CAMERON HYDROGEN ION METER Filed May 26, 1937 MM @W :9% INN tif.: I;

www .wm NS Dec. 5, 1939.

Patented Dec. s, 1939 PATENT OFFICE HYDROGEN ION LIETER Donald H. Cameron, Racine, Wis., assigner to B. D. Eisendrath Tanning Co., Chicago, lll., a

corporation of Illinois Application May 26, 1937, Serial No.. 144,873

15 Claims.

The invention relates to hydrogen ion meters and has for its principal object to provide a simple, effective and accurate meter which can easily be put into operation for the attainment of consistent measurements.

The improved meter comprises two principal units which may be located at suitable distances apart. One of these units, which may be referred to as the remote unit, includes a glass electrode of known type which is brought intov cooperation with a sample of the liquid to be tested, being immersed therein. This unit is connected to the central unit by means of a cable which includes numerous conductors. The central or main unit comprises potentiometers and other electrical devices which cooperate in the determination of the measurement.

The invention will fully be understood from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings, in which:

Figure 1 is an elevational View showing the two units which constitute the apparatus;

Fig. 2 is a wiring diagram, and

Fig. 3 is a sectional View through the housing of the remote unit.

Referring to the drawings, the reference numeral l0 designates the glass electrode which is rupported from a housing I I by means of a clamp I2. This electrode is adapted to be immersed in a sample of liquid contained within a sample cup I3 which may be supported below the glass electrode Il!` by means of a movable shelf lMl. The housing I I is connected by means oi. a cable I5, which includes eight conductors, to the main unit I6. This main unit may suitably comprise an instrument board Il upon which is mounted a suitable receptacle I8 for the reception of prongs I9 of a plug 20 secured to the end of the cable I5. Thus, the remote unit and the central or control unit may be readily separated and connected again.

The cable I5 may be of any desired length. Thus, I have operated satisfactorily with cables as long as 50 feet and there is no apparent reason why the cable should not be f any length which may be necessary.

The panel Il carries a double pole, double throw switch 2l which has a central off position, a standardizing position to the left, and a reading or operating position to the right. The panel I1 also carries a galvanometer 22 which is connected to the poles of the switch 2l. When the switch 2l is thrown to the left, the galvanometer is connected to conductors 23 and 24 and when it is thrown to the right, the galvanometer is connected to the conductors 25 and 26.

The conductor 24 includes a standard cell 2l and is connected to one end of a resistance 28 and to one end of a'potentiometer 23. The conductor 5 23 is connected to one side of a cell 38, the other terminal of which is connected to a movable contact 3l which engages the resistance 28. The contact 3l is controlled by the button 32 mounted on the panel Il. The potentiometer 29 is adjustably engaged by a contact 33 which is actuated by a button 363 mounted on the panel Il. This button carries on the inner side of the panel Il a scale 35 which is Visible through a window 35 in the panel Il. The scale 35 is graduated so as to indicate the pl-I value of the liquid under test by direct reading.

The contact 33 is connected to a conductor 3l which extends through the cable I5. The conductor 3l may suitably be grounded. The end of, the potentiometer 29 remote from the conductor 2li is connected to a conductor 38 which is connected through a variable resistance 35 to the conductor 23. The conductor 38 is connected to a contact @Il which cooperates with a potentiometer All. The potentiometer 5I is connected to a cell 52. One end of the potentiometer 5I is connected to a contact 53 and to a conductor Il@ which extends through the cable i5.

The contact 58 is connected to a button I5 mounted on the panel Il. The Contact 53 cooperates with a potentiometer i5 which is con- -nected to a cell Ill. The contact 53 is controlled by a button 58 mounted on the panel Il. One end of the potentiometer t6 is connected to a 35 cell 59 which is the C battery for the thermionic tube 58 which is part of the remote unit. The other side of the cell 49 is connected to a conductor 5I which extends through the cable I5.

A battery 52, which is the B battery for 4 the thermionic tube 50, is located between the conductors 25 and 5I. The conductor 26 is connected to a contact 53 which is operated by a button 54 on the panel Il. The contact 53 co- 45 operates with a potentiometer 55 which is connected to a suitable cell 56. One end of the potentiometer 55 is connected to a conductor 5l which extends through the cable I5.

A high resistor 58 is located between the con- 50 ductor 25 and the conductor 5l. Also mounted on the panel I'l is a double pole, single throw switch 59 which controls the poles 60 and 6I.' When the switch 59 is thrown in one way, the switches are both opened and when it is thrown the other way, both the switches are closed. A conductor 62 which extends through the cable is adapted to be connected through the pole 60 to a battery 63. The other pole of the battery 63 is connected to a conductor 64 which extends through the cable. Another conductor 65 which extends through the cable is adapted to be connected by the poles 6I to a conductor 66. The conductor 66 includes a switch 61 which is normally closed and can be opened by pressing a button 68 mounted on the panel I1. The con--k ductor 66 is connected to a battery 69 in series with the switch 61. The battery 69 is also connected to a conductor 10 which extends through the cable I5. i

The remote unit will now be described in detail. This unitcomprises the housing II which is shown in section in Fig. 3. This housing may include a vertical strip 1I of Bakelite or the like,

upon which is mounted a relay 12 and a base 13 for the therxnionic tube 50 which may suitably be a Z-4 or 37 type tube. Any type of tube suitable for electrometer applications may be used. I nd that it is advantageous to maintain all of the elements of the tube at constant temperature as far as possible, and for this purpose I prefer to enclose the tube within a jacket 14 of felt or other good insulating material. An upper end 15, which may also be of Bakelite or other suitable insulating material, is rigidly carried on the upper end of the strip 1I by means of a bracket 16. This bracket also provides an opening whereby the cable I5 may pass into the housing II. At its lower end the strip 1I carries a bracket 11 which serves as a support for the glass electrode I0.

The housing comprises a cylindrical wall 18 which may suitably be of Bakelite and also a lower end member 19 through which the bracket 11 passes. The end members 15 and 19 are cemented to the cylindrical wall 18 so as to protect the elements inside the housing from humidity. Through the closure member 19 passes a conductor 88 which leads downwardly into the glass electrode I0. 'Ihe upper closuremember 15 carries a terminal 8| to which the conductor 82 is connected. This conductor also connects to a reference half-cell 83 which may suitably be of the KCl HgClz-Hg type.

This half-cell comprises a chamber 84 which contains successive layers of metallic mercury, mercuric chloride and saturated solution of potassium chloride. The potassium chloride solution communicates through a. bent tube 85-and rubber tube 86 with the lower portion of the sample cup I3. The tube 85 is provided with a stop cock 81 and the tube 86 is provided with a snap clamp 88. In the normal operation of the device the cock 81 is closed and the clamp 88 is in tube-closing position. It will be understood, however, that conductivity is maintained between the liquid in the sample cup and inthe chamber 84 through these valves at all times.

The glass electrode I may suitably be of the common bulb type and may comprise a platinum wire which is connected to the conductor 88 and extends into the liquid within the electrode which may suitably consist of deci-normal hydrochloric acid to which a small amount of quinhydrone has been added. 'I'he conductors l65 and 10 of the cable I are connected to the winding 89 of the relay 12. The armature 90 of this relay is connected to the conductor 80 and a spring 9I normally biases the armature away from a contact point 92 which is connected to conductor 44. It will thus be understood that when the relay 12 is energized the conductor 80 which is connected to the interior of the glass electrode' I0 and to the grid of the tube 50, is connected by the conductor 44 to the contact 43 and to one end of the potentiometer 4I.

Conductors 62 and 64 are connected to the heating lament of the tube 50. The conductor 51 is connected to the plate of the tube 50. The conductor 5I is connected to the cathode of the tube 50, and the conductor 31 is connected to the terminal 8| and, consequently, to the electrode 83. I prefer to connect the conductor 31 through a suitable condenser 93, which may have a capacity of 0.001 microfarad, to the conductor 80.

The measurement of pH depends upon the fact that within certain limits, that is, approximately between 0 and 9 degrees pH, the cell constituted by the electrodes I0 and 83 gives a voltage which is proportional to the pH of the liquid contained in the vessel I3. This voltage impressed upon the grid of the tube 50 gives a plate current which is proportional thereto. Consequently, if the voltage provided by the battery including the electrodes I0 and 83 is not impressed upon the grid of the tube 50 and the output of this tube is balanced by suitable manipulation of potentiometers, so that the galvanometer 22 reads zero, and then the eiect ofthe electrode is applied to the grid, the galvanometer 22 will be deected. To correct this deflection the potentiometer 29 has to be adjusted. The degree of adjustment, as shown by the dial 35, will indicate the hydrogen ion concentration numerically and directly.

The operation will now be described in detail. The'switch 59 is closed, with the result that the relay 12 is energized and conductor 80 is connected to the conductor 44. Consequently, the grid circuit includes the cathode, the conductor 5I, the C battery 49, potentiometer 46, contact 43, conductor 44, contact 92, armature 90 and conductor 80 to grid. The switch 2I is first closed to the left and the contact 3I is operated by the button 32 until the galvanometer 22 is returned to zero. In other words, the cell 30 is balanced against the standard cell 21 by varying'the resistance 28.

It may here be remarked that the potentiometer 29, of which the contact 33 is moved by the button 34 which has rigidly secured to it the scale 35, must be adjusted so as to correlate the voltage change with variation of pH. Thus, I ndthat with an apparatus of the type described each degree change in pH may give, for example, a voltage change of 59 millivolts and the potentiometer 29 should be arranged to have a potential drop of approximately 59 millivolts for each pH space unit on the dial 35. The adjustment ofl millivolts to displacement on the potentiometer 29 may be regulated by the variable resistance 39, which resistanceis then set.

The galvanometer switch is then turned to the right to operating or reading position. The points 43 and 53 are adjusted by their appropriate buttons so as to bring the galvanometer to zero. This adjustment should bring the contact 43 to approximately the center of the potentiometer 46. It will thus be seen that the voltage applied to the grid is the algabraic sum of the voltage lof cell 49 andthe eiective portion of the potentiometer 46. This voltage produces a certain plate current across the high resistance 58. The drop of potential across the resistance 58 is counter-balanced by the potential oi.' the effective part of the potentiometer 55 so that no current passes through the galvanometer. This standardization, that is, the bringing oi! the galvanometer to zero reading by manipulation of button 45, is effected before each readmg, if

necessary. v

A standard test solution, say one with a pH of 7, is placed in the test cup I3 so that the glass electrode Il! is submerged in the liquid. The dial 35 is then set to read 7, which causes a corresponding movement of the contact 33 on the potentiometer 29. The switchv 61 is then depressed by the button 68 and the relay 12 is no longer energized, so that the armature is moved away from the contact 92 by the spring 9|. Under these circumstances the grid bias is the algebraic sum of the voltages of the battery 83-l0, the voltage of the effective portion of the potentiometer 29, the voltage of the effective portion of the potentiometer 4|, the voltage of the eiective portion of the potentiometer t, and the voltage of the C battery 49.

In general, this is-a different grid bias than Was previously impressed on the tube and, consequently, the plate current is diierent and the voltage across the resistance 58 is different. The button 45 is now actuated in the appropriate direction to return again the galvanometer reading to zero. The procedure may be repeated with an unknown solution. In general, it will cause deflection of the galvanometer and if the button 3d is turned in the appropriate direction to bring the galvanometer needle to zero position, the pI-I value of the` test solution will be shown on the dial 35.

It is very important that the conductor tu, which connects the glass electrode i@ to the grid of the thermionic tube 50, should be very short to avoid picking up of stray electrical impulses which would give erratic readings. For this reason I locate the tube 5t in the same unit as the glass electrode iii. '111e variation due to the introduction of the pH battery into the grid circuit affects the plate current which is a direct current and may pass through the cable it for any desired length without' the introduction of error. Electrical control of the remote unit is eected exclusively at the main unit and no control is exercised at the remote unit with the, exception of placing the appropriate sample in the cup i3.

This application is a continuation in part of my copending application Serial No. 133,333, iiled March 27, 1937.

Although the invention has been disclosed in connection with the speciiic details of a preferred embodiment thereof, it must be understood that such details are not intended to be limitative of the invention except insofar as set forth in the y accompanying claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a compact test unit comprising a glass electrode, a thermionic tube in close proximity thereto, a short conductor connecting the glass electrode to the grid of the tube, indicating means in remote relation to said test unit, a cable adapted to connect the plate of the tube to said remote indicating means, means adjacent said tube operablel for rendering said tube eiective and ineiective, and control means adjacent said indicating means for actuating said operable means.

2. In combination, a compact test unit comprising a glass electrode, a thermionic tube in close proximity thereto, a short conductor connecting the glass electrode to the grid of the tube, a relay adjacent said tube, a conductor adapted to be connected to said grid by said relay, conductors for controlling said relay, conductors connected to said tube, indicating means in remote relation to said test unit, a cable through which pass all said conductors except the first said short conductor for connecting the unit to said remote indicating means, and means adjacent said indicating means for energizing and deenergizing said relay. Y

3. In an apparatus for measuring hydrogen ion concentration, in combination, a test unit comprising a glass electrode,y a thermionic tube in close proximity thereto, a short conductor connecting said electrode to the grid of the tube,

and a relay, an independent unit including a potentiometer and means for actuating said relay, and a cable connecting said units including a circuit adapted to connect said potentiometer to the cathode of the tube and to said electrode, said relay being adapted to eliminate. the glass electrode and the potentiometer from the circuit.

4. In an apparatus for measuring hydrogen ion. concentration, in combination, a glass electrode, a thermionic tube in close proximity thereto, a short conductor connecting said electrode to the grid of the tube, a circuit including in series, a measuring potentiometer and a standardizing potentiometer connecting said electrode to the cathode of the tube, said potentiometers being located in remote relation to said thermionic tube, and a relay located adjacent said potentiometers for eliminating the glass electrode and measuring potentiometer from said circuit.

5. In an apparatus for measuring hydrogen ion concentration, in combination, a remote unit comprising a glass electrode, a thermionic tube in close proximity thereto, a short conductor connecting said electrode to the grid oi'the tube, a control unit comprising electricaldevices for indicating electric eects and a variable potentiometer, and a cable connecting said units including conductors establishing a circuit extending between said units including said electrode and said potentiometer and connecting to the cathode of the tube, a relay in the remote unit, and means in the control unit for controlling the relay, said relay being adapted to eliminate the glass electrode and potentiometer from said circuit.

6. In an apparatus for measuring hydrogen ion concentration, in combination, a remote unit comprising a glass electrode, a thermionic tube in close proximity thereto, a short conductor connecting said electrode to the grid of the tube, a control unit comprising electrical devices for indicating electric effects, a measuring potentiometer and a standardizing potentiometer, and a cable extending between said units including conductors establishing a circuit including said electrode and said potentiometers and connecting to the cathode of the tube, a relay in the remote unit, and means in the control unit for controlling the relay, said relay being adapted to eliminate the glass electrode and measuring potentiometer from said circuit.

7. In an apparatus for measuring hydrogen ion concentration, in combination, a glass electrode, a thermionic tube, a liquid-tight housing enclosing said tube, a short conductor extending through said housing and connecting the glass electrode to the grid of the tube a further conductor, and circuit-changing means within said housing, said circuit-changing means being adapted to connect said short conductor to said further conductor, and means remote from the glass electrode for actuating the circuit-changing means.

8. In an apparatus for measuring hydrogen ion concentration, in combination, a glass electrode, a test vessel adapted to support liquid around said electrode, a reference half cell adapted to cooperate with the liquid in said vessel, a housing in close propinquity to said glass electrode, a thermionic tube in said housing heat insulating material in said housing enc osing said tube, a short conductor passing through said housing connecting the electrode to the grid of the tube, a condenser located between the reference half cell and said conductor, and conductors extending into said housing and connected to elements of the tube.

9. In an apparatus, for measuring hydrogen ion concentration, in combination, a glass electrode, a testy vessel adapted to support liquid around said electrode, a reference half cell adapted to' cooperate with the liquid in said vessel, a housing in close propinquity to said glass electrode, a thermionic tube in said housing, heat insulating material in said housing enclosing said tube, a short conductor passing through said housing connecting the electrode to the grid of the tube, a condenser located between the reference half cell and said conductor, and a single cable including conductors connected to the cathode heater and plate of said tube.

l0. In an apparatus for measuring hydrogen ion concentration, in combination, a glass electrode, a thermionic tube, a liquid-tight housing enclosing said tube, a short conductor extending through said housing and connecting the glass electrode to the grid of the tube, a relay within the housing, a conductor extending into the housing adapted to be connected to the grid by said relay, and conductors extending into the housing to energize the relay.

11. In an apparatus for measuring hydrogen ion concentration, in combination, a glass electrode, a test vessel adapted to support liquid around said electrode, a reference half cell adapted to cooperate with the liquid in said vessel, a housing in close propinquity to said glass electrode, a thermionic tube in said housing, heat insulating material in said housing enclosing' said tube, a short conductor passing through said housing connecting the electrode to the grid of the tube, a condenser located between the reference half cell and said conductor, a relay in said housing, a conductor extending into said housing and adapted to be connected to said grid by said relay, and other conductors extending into said housing and connected to elements of the tube and to said relay.

12. In an apparatus for measuring hydrogen ion concentration, in combination, a. glass electrode, al thermionic tube adjacent thereto, a short conductor connecting the glass electrode to the grid of the tube, a further conductor, a circuitchanging means adjacent said tube and glass electrode, said circuit-changingy means being adapted to connect said short conductor to said further conductor, and means remote from the glass electrode for actuating the current-changing means.

13. In an apparatus for measuring hydrogen ion concentration, in combination, a glass electrode, a thermionic tube adjacent thereto, a short conductor connecting the glass electrode to the grid of the tube, a relay adjacent said tube and glass electrode, a conductor adapted to be connected to the grid of the tube by said relay, and conductors connected to said relay to energize the same.

14. Apparatus for measuring hydrogen ion concentration comprising a test unit, a control unit in remote relation thereto, and a cable connecting said units, said test unit including a glass electrode, a reference half cell adapted with the liquid to be testedy to constitute a cell, a thermionic tube, a short conductor connecting said glass electrode to the thermionic tube so as to control the plate current of said tube, said control unit including a plurality of variable voltage supplying means, calibrated means for controlling one of said Variable voltage supplying means, a galvanometer, means tending to supply opposite current to the galvanometer, said cable comprising conductors connecting said cell and said plurality of variable voltage supplying means in circuit, a conductor for short-circuiting last said variablevoltage supplying means and said cell in last said circuit, and conductors for supplying the plate current to said galvanometer.

15. In an apparatus for measuring hydrogen ion concentration, in combination, a test unit, a control unit in remote relation thereto, and a cable connecting said units, said test unit including a glass electrode, a reference half cell adapted to cooperate with the liquid being tested to provide a voltage producing cell, and a thermionic tube adjacent said glass electrode, said control unit including means for supplying a plurality of voltages, a resistance and a galvanometer, said cable including a conductor adapted to connect the plate of said tube to said galvanometer, said resistance and to one of said means for supplying voltage, and conductors completing a circuit including the grid and plate of said tube, said cell and a plurality of said voltage-supply ing means, and a conductor for short-circuiting said cell and one of said voltage supplying means out of last said circuit.

DONALD H. CAMERON. 

